The road was closed to allow emergency services deal with the incident and for officers from the Roads Policing Unit to investigate the circumstances of the collision.

The outside lane was re-opened at around 12.45am, while the other two lanes were re-opened by Highways England at 3.25am.

Senior investigating officer Sgt Graeme Hughes, from the Serious Collision Investigation Unit at Three Mile Cross, said: "I would like to hear from anyone who saw this collision, or saw the black Citroen people carrier before it left the carriageway.

"Some witnesses came forward at the scene, but if you have information which could assist the investigation and have not yet spoken to police please contact us."

Spokesman for South Central Ambulance Service David Gallagher confirmed it sent a 'significant amount of resources' to the scene of the incident after being alerted at 10.02pm to a car coming off the motorway.

A BASICS (British Association for Immediate Care) doctor was sent out, along with two ambulance officers, two hazardous-area response teams, five ambulances and the Surrey air ambulance.

Anyone with information about the collision should contact the 24-hour Thames Valley Police service desk on 101 quoting URN 1393 12/10.

If you don’t want to speak directly to the police you can contact Crimestoppers anonymously on 0800 555111.